Venous thrombosis is an uncommon disorder in childhood with an incidence of about 1 in 100,000 children (ages 0 to 18 years). Multiple clinical underlying conditions as well as congenital prothrombotic disorders contribute to the development of pediatric venous thromboembolic disease. The majority of thrombi are catheter-related and therefore situated in the upper venous system. Diagnosis of thrombosis in either the upper or lower venous system is most frequently made by noninvasive radiographic techniques, especially ultrasonography. Children are treated according to recommendations based on small pediatric studies and guidelines adapted from adult patient protocols. The long-term complications, including mortality, recurrence, and the post-thrombotic syndrome, seem to be considerable. Because the incidence of pediatric venous thrombosis will probably rise due to the increased use of central venous catheters and the increased survival of children with chronic diseases associated with a prothrombotic state, prevention of this disease will become an important issue.